We and others have identified several genes that promote cochlear noise injury in mice, and whose homologues may promote similar injury in humans. We now have evidence for a major effect quantitative trait locus (QTL) in mice that influences not the extent of noise injury, but rather the cellular distribution of noise injury. Hours after a moderate noise exposure (4-45 kHz, 110 dB SPL, 2 hrs), CBA/J mice show a reduction in the endocochlear potential (EP), as well as characteristic pathology within stria vascularis, spiral ligament, and spiral limbus. Although the EP recovers over time, the injury to stria and limbus is permanent. C57BL/6J (B6) mice, by contrast, show no significant acute EP reduction, and minimal acute or permanent cellular pathology. B6/CBA F1 hybrid mice respond to noise in a manner similar to the CBA parent strain, suggesting that one or a few dominant loci govern all facets of the injury phenotype. N2 backcross mice show the same constellation of noise pathology, and suggest linkage of the noise phenotype to the region containing the agouti locus on mouse chromosome 2. We HYPOTHESIZE that the linkage interval includes a gene involved in ion transport through the lateral stria (basal and intermediate cells) and limbus. The gene may code for an ion channel whose conductance is down-regulated by hypoxia or oxidative stress. Our findings point to novel genetic modulation of cochlear ion homeostasis during noise stress. The gene(s) and processes involved may impact the long term stability of cochlear noise injury and the accumulation of injury that presents as presbycusis. Our SPECIFIC AIMS are 1) To determine the cellular basis of EP reduction after noise exposure in CBA mice, 2) To examine the correlation of noise-related cellular pathologies of stria, spiral ligament, and limbus that comprise the CBA phenotype, and 3) To identify candidate gene(s) underlying CBA versus B6 strain differences in the effects of noise. RELEVANCE TO PUBLIC HEALTH: The cochlea contains many cell types whose functions are not known, but probably help maintain an appropriate ionic environment so that sensory cells can survive and respond sensitively to sound. Our work points to one or more genes that profoundy impact the distribution of noise injury in non-sensory cells. The gene, and the processes in which it is involved, may affect the long-term stability of cochlear injury, and the accumulation of injury that may be diagnosed as presbycusis. [unreadable] [unreadable] [unreadable]